bugfix: Fix issues after merging

Author: tgodzik

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -131,12 +131,12 @@ object CompilationUnit {
     unit1
   }
 
-  /** Create a compilation unit corresponding to an in-memory String. 
+  /** Create a compilation unit corresponding to an in-memory String.
    *  Used for `compiletime.testing.typeChecks`.
    */
   def apply(name: String, source: String)(using Context): CompilationUnit = {
     val src = SourceFile.virtual(name = name, content = source, maybeIncomplete = false)
-    new CompilationUnit(src, null)
+    new CompilationUnit(src)
   }
 
   /** Create a compilation unit corresponding to `source`.

compiler/src/dotty/tools/dotc/core/Phases.scala

@@ -210,7 +210,7 @@ object Phases {
     private var myPostTyperPhase: Phase = _
     private var mySbtExtractDependenciesPhase: Phase = _
     private var myPicklerPhase: Phase = _
-    private var mySetRootTreePhase: Phase = uninitialized
+    private var mySetRootTreePhase: Phase = _
     private var myInliningPhase: Phase = _
     private var myStagingPhase: Phase = _
     private var mySplicingPhase: Phase = _